Field of the Invention
The present invention relates to an image processing apparatus and an image processing method that determine whether read image data, for example, is image data that has print information or is image data of a blank page that does not have print information.
Description of the Related Art
Heretofore, in a multifunction peripheral with an automatic document reader, for example, even in the case where a document printed on both sides and a document printed on one side are loaded together, both sides will be copied when double-sided copy is instructed, resulting in wasteful processing and consumption of paper and electricity. In view of this, various blank page detection methods have been devised that are intended to suppress wasteful printing and consumption of paper and toner by detecting blank pages included in read image data and deleting image data discriminated as blank.
Japanese Patent Laid-Open No. 2010-191941 proposes a blank page determination method that involves generating a histogram of pixel values from image data, counting pixels other than the background color, and determining whether the document is blank from a ratio of the counted pixels to the number of pixels for the entire image.
On the other hand, Japanese Patent Laid-Open No. 2010-178377 proposes a blank page determination method that involves detecting edge portions in image data from the image data read from the document, and determining whether the document is blank based on the proportion of the overall number of pixels occupied by the amount of edges.
However, document paper to be read includes so-called non-white paper, such as color paper and recycled paper that contains impurities. Unexpected image objects that are not recorded may also be included in the image data. For example, dust adhering to the document or reading-related noise may be included the image data. So-called show-through where the image recorded on the reverse side can be seen on the target side may also be read. These various conditions can lead to image objects being falsely recognized as a recorded image. Thus in the method disclosed in Japanese Patent Laid-Open No. 2010-191941 or Japanese Patent Laid-Open No. 2010-178377, since the color of the paper or unexpected image objects appear in the histogram or an edge is detected if an unexpected image object is a sharp image, image objects that are not originally included in the image may be falsely recognized as being included in the image. Sheets may thus be determined to not be blank even though they are blank. When noise, dust or the like, for example, are removed with the intention of preventing such false recognition, sheets are conversely may also be determined to be blank even though they are not blank.
Thus, even using the conventional technology disclosed in Japanese Patent Laid-Open No. 2010-191941 or Japanese Patent Laid-Open No. 2010-178377, it is not easy to appropriately discriminate between image data obtained by reading a document on which a small amount of text is printed and image data obtained by reading a document on which there are spot. Also, it is not easy to appropriately detect document data obtained by reading paper containing many impurities or image data obtained by reading a document that is only show-through as being blank.